Six new 4-hydroxycoumarin derivatives have been synthesized. They were characterized by UV-vis, IR, (1)H NMR, (13)C NMR, mass spectral data, elemental analysis, TLC and melting point determination. The new 4-hydroxycoumarin derivatives are studied by computational methods--DFT (B3LYP) and force field methods (MM2 and OPLS), in order to optimize their geometry and calculate quantum-chemical properties and conformational analysis. Five new 4-hydroxycoumarin derivatives were tested for cytotoxic activity in two tumor cell lines--HL-60 and EJ. The obtained results are compared with the utilized anticancer drug melphalan. Two of these compounds--ethyl 2-[(3,4-dihydroxyphenyl)(4-hydroxy-2-oxo-2H-chromen-3-yl)methyl]-3-oxobutanoate (SS-16) and ethyl 2-[(4-hydroxy-2-oxo-2H-chromen-3-yl)(3-nitrophenyl)methyl]-3-oxobutanoate (SS-21) show comparatively good cytotoxic properties. Their activity is weaker than melphalan. SS-16 seems to be more active than SS-21.